This invention relates to security seals, and more particularly, to a seal and lock employing a cable and a mechanism for securing a free end of the cable to the seal by a wedging action within a tapered housing bore employing balls and the like.
Of interest is commonly owned U.S. Pat. No. 5,222,776, incorporated by reference herein, which discloses a security seal and lock of which the present invention is an improvement. In this patent, a housing has a path for receiving a cable free end to be secured to the housing, the other cable end also being secured to the housing. A tapered cavity is in the housing through which the path passes. The path is defined by cable entrance and exit holes in the housing and a channel in the cavity. A pair of balls are in the cavity and are biased by a spring toward the entrance hole and the small transverse dimension of the cavity.
The path is such that it is intercepted by the balls which are used for locking the cable to the housing to preclude withdrawal of the cable. The entrance hole is offset from the exit hole transversely to the general cable insertion direction. The balls and the offset holes provide a path for the cable during insertion which path is inclined relative to the General insertion direction. In practice, insertion of the cable along the path through the housing is required to lock the cable free end to the housing. Withdrawal of the inserted free end is precluded by the balls jamming against the inserted cable.
Also of interest is commonly owned U.S. Pat. No. 5.820.176, incorporated by reference herein, which discloses a security seal and lock of which the present invention also is an improvement. The invention of the ""176 patent comprises a housing having a longitudinally extending bore with opposing first and second ends, at least the second end being in communication with the ambient about the housing through an aperture in the housing, the bore having a transverse dimension that decreases in direction from the first end to the second end. The housing has a channel of a transverse width in communication with and along the bore and forming a continuous path with the aperture. A first ball in the bore has a diameter smaller than the bore transverse dimension adjacent to the first end and larger than the bore transverse dimension adjacent to the second end. Bias means are in the bore at the first end for biasing the ball towards the second end. An elongated circular cylindrical flexible member is included having a free end for insertion into the bore at the second end through the aperture, the channel having a depth of at least 30% of the diameter of the elongated member. The bias means, bore, ball and elongated member are arranged such that a force on the elongated member to withdraw the cable free end from the housing bore toward the second end wedges the ball to the elongated member to the housing in the bore. Thus, the channel guides the elongated member, preferably a stranded cable having a nominal diameter of about {fraction (1/16)} inches or less, during insertion, provides a path for the member, decreases the degree of interference between the ball and the member during insertion and contributes to reducing the insertion load on the member.
The present inventors have found that although the prior designs are perfectly acceptable for cable sizes of a diameter of {fraction (1/16)} inches or less, they may experience difficulty with cables having a diameter in excess of {fraction (1/16)} inches or more. The larger cables have been found to be difficult to clamp. This resulted from an inadequate locking cooperation between the cable, the balls and the housing.
It is an object of the present invention to provide a security seal and lock which generates improved clamping between the lock housing and the locking cable.
Another object of the present invention is to provide a security seal and lock which is operable for use with locking cable having a diameter in excess of {fraction (1/16)} inches.
These objects and others are achieved by the security seal and lock of the present invention as to which the clamping and locking of the stranded cable within the housing is enhanced by increasing the frictional forces between the cable and the balls. In one aspect of the invention, the balls are provided with a rough surface finish as distinguished from the smooth polished surface finishes which have been known and practiced in the art. A second aspect of the invention contemplates coating the balls with a soft plastic to act as a friction generating surface. The invention also contemplates having the balls engage the housing in substantially a multi-point contact such as to enhance the clamping forces thus reducing the ability of the balls to rotate, which rotation might permit defeating the seal.